[PATCH v4 2/2] i2c: imx: Cancel hrtimer before clearing slave pointer

[Liem <liem16213@gmail.com>]

In i2c_imx_unreg_slave(), the slave pointer is set to NULL after
disabling interrupts.  However, a pending interrupt might already
have started the hrtimer (i2c_imx_slave_timeout) before the pointer
was cleared.  If the hrtimer fires after i2c_imx->slave is set to
NULL, the timer callback i2c_imx_slave_finish_op() will call
i2c_imx_slave_event() with a NULL slave pointer, which results in a
use-after-free / NULL pointer dereference.

Fix by canceling the hrtimer and waiting for it to complete after
disabling interrupts, before clearing the slave pointer.

Fixes: f7414cd6923f ("i2c: imx: support slave mode for imx I2C driver")
Cc: stable@vger.kernel.org
Acked-by: Carlos Song <carlos.song@nxp.com>
Signed-off-by: Liem <liem16213@gmail.com>
---
v3 -> v4: No changes, added Acked-by from Carlos Song.
---
 drivers/i2c/busses/i2c-imx.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/i2c/busses/i2c-imx.c b/drivers/i2c/busses/i2c-imx.c
index 2398c406e913..b1c6581db774 100644
--- a/drivers/i2c/busses/i2c-imx.c
+++ b/drivers/i2c/busses/i2c-imx.c
@@ -960,6 +960,7 @@ static int i2c_imx_unreg_slave(struct i2c_client *client)
 
 	i2c_imx_reset_regs(i2c_imx);
 
+	hrtimer_cancel(&i2c_imx->slave_timer);
 	i2c_imx->slave = NULL;
 
 	/* Suspend */
-- 
2.34.1